High-performance liquid chromatography (HPLC) is a method of separating mixtures (analysis of a sample) by means of a separating column, optionally including a subsequent evaluation. Using an HPLC pump, a solvent flow is produced, which transports the sample, containing the mixture to be separated, through the separating column. Separation takes place owing to chemical interactions between the constituents of the sample and the stationary phase (packing) of the column.
Before investigating or analyzing several, for example ten samples (batch) or an individual sample, in HPLC it is desirable to know in advance whether the amount of solvent present is sufficient for the next sample, as otherwise it is necessary to stop in the middle of the analysis, and the analysis of the sample becomes invalid.
However, hydrostatic measurement of levels in containers, as proposed for example in DE 198 26 487 A 1, has some decisive disadvantages, especially for use in HPLC. For example, in HPLC the density of the solvent and the cross-sectional area of the bottles are not known by the HPLC system. These values would therefore have to be entered by the user before beginning a test or a sample analysis.
The problem to be solved by the invention is therefore to devise a method and a device for measuring a volume, which provide results reliably and accurately, and operate as conveniently as possible for a user.